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CHARLES H. STOCKBRIDGE, OF. NORTHAMPTON, MASSACHUSETTS, ASSIGNOR TO Hm- SELF A ND OSMOBE '0. ROBERTS, OF SAME PLAGE.

Lezers Patent No. 84,015, [zaad Mamba 1o, 186s.

IMPROVEMENT IN BIT-HOLDER.

The Schedule referred to in these Letters Patent and making part of the same.

To all whom 'it may concern:

for Bits; and I do hereby declare the following to be a full, clear, and exact' description oi the said invention, reference being had to the annexed drawing, Inaking part of this specification, wherein- Figure 1 is a section of the tool-holder at the of the brace;

Figure 2 is an end view of the same; and

Figure 3, an exterior view of the inner portion oi' the bit-holder, the screw-sleeve being removed.

Similar marks of reference denote the. same parts.

Braces forbits have heretofore been made with a square socket for receiving the polygonall endof the tool, and with a pair of jaws,.acted upon by a sleeve having a contracted opening at the end, and screwing over said jaws, to close them around the shank of the bit or tool, as in Letters Patent granted toime, February 19, 1867.

yThe nature of my present invention consists in a spring applied to the'back ends of the clamping-jaws, to open them as the sleeve is screwed forward to release their outer ends from the bit; thereby the said jaws are kept out of the way in entering or withdrawing the bit, and said jaws are also heldv back in position by the action of said spring.

In the drawing, a is a` portion of the brace, of any usual or desired construction, within the end of which is the polygonal socket l), into which the squared end of the tool is passed, as usual. A

A cylinder, @projects beyond the socket l1, and is formed as part of the brace a and around this cylinder, c, ascrew-thread is formed, taking a similar thread on the inside of the screw-sleeve d, that is contracted or. dome-shaped at its end, terminating with an opening that allows the bit to be entered or withdrawn freely.

I form two incisions into the cylindrical portion c, on opposite sides thereof, and extending along at the sides of the socket b, in the form of a groove, with a rounded bottom, as seen in fig. l, and byV dotted lines in g. 2, and into this groove and opening, I place the clamping-jaws e e, that are shaped at their forward ends so as to grasp the shank of the tool or bit when thelsleeve d is screwed down upon them, asin my aforesaid Letters Patent; but I make the inner ends of said jaws c, with lips 2 2, and I form a neck around the outside of the socket b, at the base of the cylinder c, as seen at 3 3, iig. 3, and into this I introduce acontractile spring, i, which may be made of India rubber or of metal, in the form of a split ring.

The contraction of this ring, @opens the jaws e e, in consequence of the curved form of the bottomof the grooves containing them, so that when pressure against the outer ends of those jaws, e, by the sleeve d, is released, the` said jaws open for admitting or withdrawing the bit or tool, andthe ring yz'v being in the neck 3, holds the parts properly'in place. f`

Wha-t I claim, and desire to secure by Letters Patent,"is-f l The bit-stock, formed of the clamping-jaws e, set in grooves having curved bottoms, in combination ith the contractile spring 'i and sleeve ZZ, substantially as set forth.

In witness whereof, I have hereunto set my signature, this 24th day of April, 1868.

GHAS. H. STOGKBRIDGE.

Witnesses:

SAML T. SPAULDING. 

